GPS maps the world, but can it help me find my hotel?

An intrepid trekker learns the many uses of global positioning systems -- and crossing London's Hyde Park is just one of them.

A friend of mine has a global positioning system in his car that tells him where he is and how to get where he's going. I used to wish the little Houdini inside the receiver would come out and get acquainted. But since attending a seminar this month at the Royal Geographical Society in London, I know that GPS is the work of scientists, not magicians, and that it has extraordinary applications for travelers who read maps and cartographers who make them.

The three-day seminar is held once a year by the society's Expedition Advisory Center, which assists people about to embark on information-gathering projects around the world.

This one was taught by a formidable team of experts, including Nick McWilliam, a lecturer in geography at Anglia Polytechnic University in Cambridge, England; Richard Teeuw, who helped implement expeditions in Iceland and Kenya; and Alistair Philip, a hydrographic surveyor and oceanographer for the Royal Navy.

The 15 students who attended the seminar were an equally fascinating and varied crew, showing up for class in boots and carrying bulging backpacks as though they had just arrived from doing fieldwork in some remote place. Most were working on advanced degrees at English universities and had expeditions to plan.

One man was headed for New Caledonia to study a rare kind of crow. A doctoral candidate was doing a dissertation on pollution and urbanization on dry lake beds east of Mexico City. Another fellow hoped to get a grant to map growth patterns of an invasive underwater plant off eastern Spain.

Utterly out of my depth, I would have been happy just to find a shortcut from my Brompton Road hotel to the geographical society on the southern side of Hyde Park. Fortunately, the instructors started with a basic definition of terms even I could understand.

GPS, they told us, allows people to figure out where they are without a map, using a unit that receives signals from a constellation of satellites orbiting the Earth thousands of miles in space.

The technology is rapidly advancing. It is far more accurate and continues to improve. As a result, its applications have expanded: Freight companies have adapted GPS for tracking shipments, and commercial fishermen use it to pinpoint schools of cod and tuna on the otherwise featureless high seas.

But GPS is only the beginning, I learned. The pairing of GPS with geographical information systems (GIS), which provide data from aerial photography and light scanning, has changed our ability to understand the world as fundamentally as the discovery that the Earth is round.

Traditional maps, one of the instructors said, can show us Hyde Park. Using GPS and GIS, we can now figure out where Mrs. Smith went walking with her dog, and one day in the not- too-distant future, whether her pooch was a Dalmatian or a Lab.

Things got complicated when the instructors demonstrated how to construct elaborate maps with GIS, which entailed logging onto websites, such as one for the Global Land Cover Facility, created and maintained by the University of Maryland (www.glcf.umiacs.umd.edu). It is essentially an Internet conduit to providers of cutting-edge digital information -- including maps and images, many recently declassified by the U.S. military -- that computer users can download, often for free.

If a location, however remote, has been observed by satellite or aerial photography, it is likely to be covered by the site's data, archive, store and bank. The trick is knowing which remotely sensed information best suits your purposes.

For instance, images created by using scans of infrared light, invisible to the naked eye, are particularly good at revealing vegetation zones and, thus, could help my colleague studying invasive plants in Spain. Others, more conducive to geological studies, locate gas and mineral deposits for industry.

People who are handy enough with computers to navigate the software programs required for downloading GIS information can layer image upon image, resulting in astonishingly comprehensive maps.

By that part of the seminar, I was hopelessly lost. But frequent coffee and tea breaks were built into the schedule, as well as field excursions into Hyde Park, which we were told to pretend was a remote, uncharted region of Africa's Serengeti. We used GPS receivers to mark way points; back in the classroom, we put the way points into our computers, yielding maps of our routes, which seemed miraculous to a garden-variety traveler like me.

When the seminar ended, most of my colleagues had made important strides in planning their projects, far afield. I was just headed back to my hotel, taking a shortcut I discovered through trial and error. But by that time, I knew why and how I could have found my way across the grounds of Holy Trinity Church near Brompton Road and through Ennismore Mews behind it, with a GPS receiver.

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Susan Spano also writes "Postcards From Paris," which can be read at latimes.com/susanspano.